Brown J A, Segal H L
J Biol Chem. 1977 Oct 25;252(20):7151-5.
The uptake of macromolecular markers by fluid pinocytosis in the rat yolk sac was inhibited by glucagon, with half-maximal effect at a hormone concentration of approximately 3 X 10(-8) M. Glucagon had no effect on the cellular distribution of the marker subsequent to its uptake. Rates of uptake promptly returned to normal when the yolk sacs were transferred from a glucagon-containing to a glucagon-free medium. Epinephrine also inhibited, but only at much higher concentrations. The effect of the latter was augmented by theophylline. Insulin (10(-6) M) had no effect when added alone or with an inhibitory level of glucagon (10(-7) M). The presumption that the hormone effect was mediated by cyclic AMP was supported by the findings that the cellular levels of cyclic AMP were elevated in the presence of glucagon and that dibutyryl cyclic AMP could replace glucagon as an effective inhibitor. The conclusion that the hormone effect was on uptake rather than on subsequent regurgitation was based on the linearity of accumulation in both the presence and absence of glucagon and the inability of glucagon to stimulate loss of invertase from preloaded cells. Colchicine and vinblastine also inhibited uptake. This finding and those of others which are discussed suggest the possibility that effects of cyclic nucleotides on certain cell functions may involve their regulation of microtubular status.
胰高血糖素抑制大鼠卵黄囊中大分子标记物通过液体胞饮作用的摄取，在激素浓度约为3×10⁻⁸M时产生半数最大效应。胰高血糖素对标记物摄取后在细胞内的分布没有影响。当卵黄囊从含胰高血糖素的培养基转移到不含胰高血糖素的培养基中时，摄取速率迅速恢复正常。肾上腺素也有抑制作用，但仅在高得多的浓度下。茶碱可增强后者的作用。单独添加胰岛素（10⁻⁶M）或与抑制水平的胰高血糖素（10⁻⁷M）一起添加时均无作用。细胞内环磷酸腺苷（cAMP）水平在胰高血糖素存在时升高，且二丁酰环磷酸腺苷可替代胰高血糖素作为有效抑制剂，这些发现支持了激素效应由环磷酸腺苷介导的推测。激素效应作用于摄取而非随后的反流这一结论基于在有和没有胰高血糖素的情况下积累的线性关系以及胰高血糖素无法刺激预加载细胞中蔗糖酶损失的能力。秋水仙碱和长春花碱也抑制摄取。这一发现以及文中讨论的其他发现提示，环核苷酸对某些细胞功能的影响可能涉及其对微管状态的调节。
